Do you mean that you want to double the time that an event is seen, and that a loop would be acceptable? If that is what you mean, a script is unnecessary. Simply drag the right border of an event, and pull it right to cover the desired time period. The item will repeat just as if it was looping.

Vegasaur's Quick Properties has an event tab that you can set playback rate to .5 and check the "adjust length". You can apply it to all your events at once! Let me know if that helps. Thanks!
DavidEon